Wow! Congrats on your purchase. I think SS-Agile's are FANTASTIC
(even though I've never even seen one)
Your 2007 will be shorter (easy to park) and more fuel efficient than the upcoming 2008's. RT never sold the '07 SS-Agile in Canada. Rumor has it that will change with the 2008's.
Yes, you'll need to check the tank monitor and run the macerator when the tank is getting full. Trying to trickle water through the macerator would probably lead to clogged pipes.
I added a macerator on my 190P. I put a wireless remote switch on it. I got the switch from Wal-Mart for around $20 and it was rated 20 amps - perfect for the pump. It worked from inside my RT
In a moderate freezing environment my guess is that a minimum 50% RV antifreeze ratio to waste water should keep the pump from being damaged.
I didn't see an SS-Agile owner manual on Roadtrek's site yet.